1. Field of the Invention
The present invention is directed to an electrophotographic printer for printing a final image carrier, having a transport for transporting the final image carrier, a first printer unit for generating a first toner image on the basis of a first arrangement of color particles on a first photoconductor, at least one further printer unit for generating a further toner image on the basis of a further arrangement of color particles on a further printer, and a transfer apparatus for direct or indirect transfer of the first toner image from the first photoconductor and of the further toner image from the further photoconductor onto a surface section of the front side of the final image carrier.
2. Description of the Related Art
The term a color separation generally refers to a toner image that was applied by a single developer station. A multi-colored print image consequently arises by superimposition of a plurality of color separations.
A printer which uses color separation is disclosed, for example by European published application EP 0 659 569 A1. Given the printer described therein, the first single-color toner image (or color separation) is fixed by the first printer unit before the second toner image, which is likewise of a single-color, is applied onto the already fixed, first toner image. An exactly registered multi-color printing is not possible with the known printer since it cannot be assured that the two toner images are printed exactly on the same surface section of the carrier material. As a result thereof, the picture elements of the first toner image and of the second toner image may also not be aligned exactly relative to one another. The result is that undesired superimpositions or empty spaces between picture elements of different toner images arise (this also being known as registration error). High quality color printing is ultimately not possible. Given graduated, planar color printing, color errors and color seams arise. Further, unsharp and/or color-falsified image details arise in the region of the lines and written characters when printing lines and written characters.
The printer according to the above-cited published application is also inflexible with respect to an being adopted to different printing jobs. When, for example, printing is to be carried out with only one color, then the second printer according to said published application is superfluous. Moreover, a color pallet of four predetermined colors can only be selected when printing with the printer according to the European patent document EP 0 658 569 A1.
Published German application DE 44 34 081 A1 discloses a printer for multi-color printing that contains four printer units, each having a respective photoconductor. The apparatus disclosed therein for avoiding registration errors requires a complicated adjustment procedure wherein what are referred as eccentricity phases must be taken into consideration.